A hospital's infection-control team rejects a newly installed door package because the coating cannot withstand the chlorine-based disinfectant on their approved cleaning list — the finish chalks and dulls within weeks. The doors themselves were fine; the surface specification was not. In healthcare, the finish is not decoration: it is the working surface that gets disinfected several times a day for twenty years.

14.1 Powder coating: the healthcare default

Powder coating is a dry thermoset powder (typically epoxy-polyester hybrid for interiors) applied electrostatically and cured in an oven at roughly 180–200 °C, forming a continuous film of about 60–90 µm. For medical doors it offers:

  • A hard, non-porous, seamless surface with no brush marks or thin edges typical of wet paint
  • Good chemical resistance against common hospital disinfectants — but this must be verified, not assumed; coating chemistries differ, so require the manufacturer's resistance data against the facility's actual cleaning agents
  • Wide colour range (RAL system) for wayfinding and department coding
  • Qualicoat-class pre-treatment on a galvanized substrate gives a duplex corrosion system

Limitations: damage down to bare metal cannot be touched up invisibly on site; deep scratches in wet areas need professional repair. Specify coated-galvanized rather than coated bare CRS so that chips do not become rust sites.

14.2 Stainless steel finishes

Stainless needs no coating; its hygienic quality depends on surface finish:

  • Brushed / satin (No. 4) — the healthcare standard; hides fingerprints and minor scratches, easy to wipe.
  • 2B mill finish — smooth but dull; acceptable for low-visibility areas.
  • Mirror / polished — highest cleanability but shows every smudge; mostly decorative.
  • Electropolishing — electrochemically smooths the microscopic surface, reducing bacterial adhesion sites and improving corrosion resistance; worth specifying for pharmaceutical and sterile-suite doors.

Stainless can still stain or tea-stain from chlorides and harsh chemicals; it needs cleaning and occasional passivation, not zero maintenance.

14.3 Corrosion protection as a system

Think in layers: substrate (galvanized or stainless) → pre-treatment (phosphate or zirconium conversion) → coating. A premium powder over unprepared CRS fails before a mid-grade powder over properly pre-treated galvanized steel. Cut edges, drilled holes and weld zones are the weak points — good practice is zinc-rich touch-up or edge sealing at the factory.

14.4 Antimicrobial treatments — and what ISO 22196 actually says

Many suppliers offer "antibacterial" powder coatings with silver-ion or other additives. The standard test cited is ISO 22196, and its scope is frequently oversold. Per the standard, ISO 22196:2011 "specifies a method of evaluating the antibacterial activity of antibacterial-treated plastics, and other non-porous, surfaces of products." Key facts buyers should know:

  • It is a laboratory method: treated and untreated sample surfaces are inoculated with bacteria (typically Staphylococcus aureus and Escherichia coli), held under a film for 24 hours, and the reduction in recovered bacteria is measured.
  • It measures antibacterial activity on the surface under test conditions — it does not prove reduced infection rates, does not cover viruses or fungi, and says nothing about performance after years of abrasion and disinfection.
  • A result is only meaningful for the specific tested coating formulation; a certificate for one product does not transfer to another colour or batch chemistry.

Antimicrobial coatings are a useful supplement to — never a substitute for — the facility's cleaning protocol.

14.5 Common mistakes

  • Specifying colour but not coating chemistry, thickness or disinfectant resistance
  • Accepting "ISO 22196 certified" without asking which surface, which organisms and which lab report
  • Mirror-polished stainless on high-touch doors (maintenance complaint within a month)
  • Field touch-up of powder coat with incompatible wet paint

Practical checklist

  • [ ] Powder coat on pre-treated galvanized substrate; film thickness stated
  • [ ] Written chemical resistance data vs. the facility's disinfectant list
  • [ ] Stainless: grade (304/316) and finish (No. 4 or electropolished) specified
  • [ ] Antimicrobial claims backed by an ISO 22196 lab report for that exact coating
  • [ ] Repair and touch-up procedure agreed in the O&M manual

Sources